1. Technical Field
The present invention relates to a tuning fork resonator element and a tuning fork resonator using a piezoelectric material.
2. Related Art
A tuning fork resonator element is manufactured by forming a tuning fork type shape from a piezoelectric substrate and an electrode on the front surface, utilizing a photolithography technique.
In particular, formation methods of electrodes and support methods for tuning fork resonator elements have recently been studied for the purposes of improvements in performance and productivity of thinner and miniaturized tuning fork resonator elements.
A first example of related art, JP-A-2006-339729, describes that in order to improve the accuracy of light exposure for a crotch portion of a tuning fork, a mask is brought into contact with a resist formed on an electrode formation surface of a tuning fork resonator element and a light source is inclined at a predetermined angle so that light applied to an inclined surface of a crotch portion formed between resonating arms is made closer to the direction of applying the light perpendicularly to the inclined surface, thus performing light exposure.
Also, a mount structure where a support arm is joined to and supported with a base is disclosed.
In a second example of related art, JP-A-2001-156584, it is disclosed that side end surfaces of a piezoelectric element chip are formed to be outwardly convex such that inclined surfaces having slopes of 5 to 20 degrees with respect to a direction perpendicular to the upper surface or the lower surface intersect with each other in the center portion in the thickness direction from the upper surface and the lower surface.
It is also disclosed that in forming a resist for forming electrodes for this purpose, applying ultraviolet light from right above or at an angle of 0 to 30 degrees enables the resist on the side end surfaces to be exposed to light with reliability.
Thus, it is disclosed that electrodes can be accurately formed in side end surfaces, particularly in the crotch portion.
This eliminates a short-circuit between electrodes, thus preventing defective products.
It is also disclosed that the amount of polishing is controlled by jetting a solid-gas two-phase jetting flow from a jetting opening of a nozzle to cause side end surfaces of a piezoelectric element chip to be inclined.
A third example of related art, JP-A-54-151391, describes that the size of an etching residue in the crotch portion of a tuning fork is relevant to the space and thickness of the resonating arm.
A fourth example of related art, JP-A-2006-311088, discloses that two supporting arms are each joined to two points of electrode portions of a substrate through a conductive adhesive.
In the first related art example, as shown in FIG. 9, a tuning fork resonator element has a structure in which two support arms 91 are provided at positions sandwiching two resonating arms 11 and the support arms 91 are each mounted on a base through a conductive adhesive 92.
With such a structure, a portion that is likely to function as a leakage path is the crotch portion of the resonating arm.
Therefore, as disclosed in the third related art example, an etching residue in the crotch portion of a resonating arm is formed using the space and thickness of the resonating arm, allowing a resist of the crotch portion to be exposed to light if the exposure is perpendicular to the substrate to prevent a short-circuit between electrodes.
Alternatively, an etching residue in the crotch portion of a resonating arm is formed by the adjustment of conditions such as etchant concentration and etching time, allowing a short-circuit between electrodes of the crotch portion to be prevented.
However, with a structure of the first related art example, if an impact is applied from the outside, leading ends of the resonating arms 11 and leading ends of a base portion are dramatically displaced up and down with a mount portion serving as a fulcrum as shown in a side view in FIG. 10.
Therefore, a clearance between a resonator element and a package as well as a clearance between a resonator element and a lid need to be large.
In the structure of the first related art example, however, if an impact from the outside is applied, the leading end of the resonating arm 11 and the leading end of the base portion are largely displaced with the mount portion serving as the fulcrum, as shown in the side view of FIG. 10.
Therefore, a clearance between the resonator element and the package and a clearance between the resonator element and the lid need to be large.
If a structure of fixing a resonator element by using a conductive adhesive at two points of each support arm as in the fourth related art example is employed, it is difficult to provide a card-type tuning fork resonator needed to have a thickness of 0.4 mm or less so as to ensure a clearance between the resonator element and the package and a clearance between the resonator element and the lid.
The use of the inclined light exposure disclosed in the first related art example and a method of jetting a solid-gas two-phase jetting flow disclosed in the second related art example degrades the throughput to increase the manufacturing cost as well as productivity.